Recently, patent foramen ovale (hereinafter referred to as PFO) has been identified as a cardiac factor in strokes and migraines. The PFO is a symptom in which the oval foramen (foramen ovale) for shortcircuiting blood between the left and right sides in the heart in the fetal period of a person's life remains even after the person has gown up. It is said that 20-30% of grown-up people have this disease.
The foramen ovale occurs at a septum secundum (Septum Secundum, hereinafter, referred to as atrial septum secundum) of the heart. The pressure on the left atrium side normally exceeds the pressure on the right atrium side in the heart and so the foramen ovale is occluded by a septum primum (Septum Primum, hereinafter, referred to as foramen ovale valve). However, when the pressure on the right atrium side exceeds the pressure on the left atrium side on a strain occasion (for example, when coughing, when holding on) or the like, the foramen ovale valve opens to the left atrium side and blood can flow from the right atrium side (venous side) into the left atrium side (arterial side). When a thrombus is included in this blood, the thrombus is shifted from the venous side to the arterial side, flows in a route of left atrium→left ventricle→aorta→brain, and can become a factor for a stroke, migrane or the like.
Examples of the treatment of such a disease include pharmacotherapy (aspirin, warfarin, or the like), closure of the PFO by percutaneous catheterization, and open heart surgery by extracorporeal circulation. Pharmacotherapy is the treatment which should be selected first, but it can be difficult to manage the dosage, and bleeding may not cease easily during the dosage. Percutaneous catheterization and the open heart surgery are radical treatments and remove the fear of recurrence, though they are invasive procedures. At the present stage, of these closure procedures, open heart surgery is more assured. However, taking into account the risk attendant on the extracorporeal circulation and the magnitude of the invasion attendant on skin incision, the treatment by percutaneous catheterization is more desirable, if it produces the same effect as that of the open heart surgery.
Devices for closure by use of percutaneous catheterization can be used also in the cases of closing a defect, such as cogenital atrial septal defect (ASD), PFO, ventricular septal defect (VSD), patent ductus arteriosus (PDA), etc. The conventional devices, however, are based on clamping the SP and the SS by use of a disk-like membrane or anchor member for closing the defect, and they are left indwelling in the patient's body.
The membrane and the anchor member are foreign matters for the body, and thrombi are liable to deposit thereon. Particularly, when a thrombus deposits on the disk-like membrane on the side of the left atrium of the heart, it may flow downstream to cause stroke, or may break the SP which is small in wall thickness. In addition, these members may be positionally deviated, instead of being positionally fixed in the state of clamping the relevant tissues.
Consequently, recently, there has been proposed a PFO closing device which is described in Patent Document 1 (U.S. Application Publication No. 2006/0271030) and in Patent Document 2 (U.S. Application Publication No. 2007/0093804).
The PFO closing device described in Patent Document 1 of U>S> Application Publication No. 2006/0271030 is such that a suctionable suction portion is provided at a distal portion of a catheter thereof; a foramen ovale valve is sucked and pulled from the right atrium side by this suction portion and closed; and tissue is fused by applying energy by way of an electrode portion.
The PFO closing device described in Patent Document 2 of U.S. Application Publication No. 2007/0093804 is such that an expandable/shrinkible balloon is provided at a distal portion of the catheter thereof and at the same time, a suctionable suction portion is provided at the distal side of the balloon. While holding an atrial septum secundum by the balloon from the right atrium side, a foramen ovale valve is sucked and pulled by the suction portion and closed; and tissue is fused by applying energy by way of an electrode portion.
However, in either closing device of Patent Documents 1 and 2 mentioned above, there is a concern that the foramen ovale valve may not be sucked and blood is sucked excessively if the foramen ovale valve is distanced from the atrial septum secundum at the time of sucking. Also, in either closing device of the Patent Documents 1 and 2, the positioning of the electrode portion of the catheter is executed by a guide wire which is inserted into the foramen ovale, but the center of the suction portion or the electrode portion does not always coincide with the center of the foramen ovale, so that there is a problem that it is difficult to arrange the electrode portion at a desirable region for being applied with energy.